# Yahoo! UI Library

### animation 2.8.1

Yahoo! UI Library > animation > AnimMgr.js (source view)
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    /**
     * Handles animation queueing and threading.
     * Used by Anim and subclasses.
     * @class AnimMgr
     * @namespace YAHOO.util
     */
    YAHOO.util.AnimMgr = new function() {
        /**
         * Reference to the animation Interval.
         * @property thread
         * @private
         * @type Int
         */
        var thread = null;

        /**
         * The current queue of registered animation objects.
         * @property queue
         * @private
         * @type Array
         */
        var queue = [];

        /**
         * The number of active animations.
         * @property tweenCount
         * @private
         * @type Int
         */
        var tweenCount = 0;

        /**
         * Base frame rate (frames per second).
         * Arbitrarily high for better x-browser calibration (slower browsers drop more frames).
         * @property fps
         * @type Int
         *
         */
        this.fps = 1000;

        /**
         * Interval delay in milliseconds, defaults to fastest possible.
         * @property delay
         * @type Int
         *
         */
        this.delay = 1;

        /**
         * Adds an animation instance to the animation queue.
         * All animation instances must be registered in order to animate.
         * @method registerElement
         * @param {object} tween The Anim instance to be be registered
         */
        this.registerElement = function(tween) {
            queue[queue.length] = tween;
            tweenCount += 1;
            tween._onStart.fire();
            this.start();
        };

        /**
         * removes an animation instance from the animation queue.
         * All animation instances must be registered in order to animate.
         * @method unRegister
         * @param {object} tween The Anim instance to be be registered
         * @param {Int} index The index of the Anim instance
         * @private
         */
        this.unRegister = function(tween, index) {
            index = index || getIndex(tween);
            if (!tween.isAnimated() || index === -1) {
                return false;
            }

            tween._onComplete.fire();
            queue.splice(index, 1);

            tweenCount -= 1;
            if (tweenCount <= 0) {
                this.stop();
            }

            return true;
        };

        /**
         * Starts the animation thread.
    	* Only one thread can run at a time.
         * @method start
         */
        this.start = function() {
            if (thread === null) {
                thread = setInterval(this.run, this.delay);
            }
        };

        /**
         * Stops the animation thread or a specific animation instance.
         * @method stop
         * @param {object} tween A specific Anim instance to stop (optional)
         * If no instance given, Manager stops thread and all animations.
         */
        this.stop = function(tween) {
            if (!tween) {
                clearInterval(thread);

                for (var i = 0, len = queue.length; i < len; ++i) {
                    this.unRegister(queue[0], 0);
                }

                queue = [];
                thread = null;
                tweenCount = 0;
            }
            else {
                this.unRegister(tween);
            }
        };

        /**
         * Called per Interval to handle each animation frame.
         * @method run
         */
        this.run = function() {
            for (var i = 0, len = queue.length; i < len; ++i) {
                var tween = queue[i];
                if ( !tween || !tween.isAnimated() ) { continue; }

                if (tween.currentFrame < tween.totalFrames || tween.totalFrames === null)
                {
                    tween.currentFrame += 1;

                    if (tween.useSeconds) {
                        correctFrame(tween);
                    }
                    tween._onTween.fire();
                }
                else { YAHOO.util.AnimMgr.stop(tween, i); }
            }
        };

        var getIndex = function(anim) {
            for (var i = 0, len = queue.length; i < len; ++i) {
                if (queue[i] === anim) {
                    return i; // note return;
                }
            }
            return -1;
        };

        /**
         * On the fly frame correction to keep animation on time.
         * @method correctFrame
         * @private
         * @param {Object} tween The Anim instance being corrected.
         */
        var correctFrame = function(tween) {
            var frames = tween.totalFrames;
            var frame = tween.currentFrame;
            var expected = (tween.currentFrame * tween.duration * 1000 / tween.totalFrames);
            var elapsed = (new Date() - tween.getStartTime());
            var tweak = 0;

            if (elapsed < tween.duration * 1000) { // check if falling behind
                tweak = Math.round((elapsed / expected - 1) * tween.currentFrame);
            } else { // went over duration, so jump to end
                tweak = frames - (frame + 1);
            }
            if (tweak > 0 && isFinite(tweak)) { // adjust if needed
                if (tween.currentFrame + tweak >= frames) {// dont go past last frame
                    tweak = frames - (frame + 1);
                }

                tween.currentFrame += tweak;
            }
        };
        this._queue = queue;
        this._getIndex = getIndex;
    };

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